Hard-disk drives (HDD) are the storage medium of choice for computers and related devices. They are found in most desktop and laptop computers, and may also be found in a number of consumer electronic devices, such as media recorders and players, and instruments for collecting and recording data. Hard-disk drives are also deployed in arrays for network storage.
Hard-disk drives store information magnetically. The disk in a hard-disk drive is configured with magnetic domains that are separately addressable by a magnetic head. The magnetic head moves into proximity with a magnetic domain and alters the magnetic properties of the domain to record information. To recover the recorded information, the magnetic head moves into proximity with the domain and detects the magnetic properties of the domain. The magnetic properties of the domain are generally interpreted as corresponding to one of two possible states, the “0” state and the “1” state. In this way, digital information may be recorded on the magnetic medium and recovered thereafter.
The magnetic medium in a hard-disk drive is generally a glass, composite glass/ceramic, or metal substrate, which is generally non-magnetic, with a magnetically susceptible material deposited thereon. The magnetically susceptible material is generally deposited to form a pattern, such that the surface of the disk has areas of magnetic susceptibility interspersed with areas of magnetic inactivity. The non-magnetic substrate is usually topographically patterned, and the magnetically susceptible material deposited by spin-coating or electroplating. The disk may then be polished or planarized to expose the non-magnetic boundaries around the magnetic domains. In some cases, the magnetic material is deposited in a patterned way to form magnetic grains or dots separated by a non-magnetic area.
Such methods are expected to yield storage structures capable of supporting data density up to about 1 TB/in2, with individual domains having dimensions as small as 20 nm. Where domains with different spin orientations meet, there is a region referred to as a Bloch wall in which the spin orientation goes through a transition from the first orientation to the second. The width of this transition region limits the areal density of information storage because the Bloch wall occupies an increasing portion of the total magnetic domain.
To overcome the density limits due to Bloch wall widths in continuous magnetic thin films, the domains can be physically separated by a non-magnetic region (which can be narrower than the width of a Bloch wall in a continuous magnetic thin film). Conventional approaches to create discrete magnetic and non-magnetic areas on a medium have focused on forming single bit magnetic domains that are completely separate from each other, either by depositing the magnetic domains as separate islands or by removing material from a continuous magnetic film to physically separate the magnetic domains. A substrate may be masked and patterned by a mask material, and a magnetic material deposited over exposed portions, or the magnetic material may be deposited before masking and patterning, and then etched away in exposed portions. In either case, the topography of the substrate is altered by the residual pattern of the magnetic regions. Because the read-write head of a typical hard-disk drive may fly as close as 2 nm from the surface of the disk, these topographic alterations can become limiting. Furthermore, during the depositing, etching and patterning processes of manufacturing the hard-disk drives, the substrate may experience multiple heating and thermal processes. The thermal energy provided to the substrate during these processes may adversely harden the mask material or disrupt alignment of atomic spins arranged in the magnetic regions. Hardening the mask layer may result in residuals mask material remaining on the substrate after the mask layer stripping process, thereby contaminating the structure formed on the substrate. Additionally, excessive heating may cause re-crystallization of materials, which may adversely change or modify the magnetic properties intended to be formed in the device, thereby causing degradation of the magnetic performance of the hard-disk drives.
Thus, there is a need for a method of patterning magnetic media to form magnetic and non-magnetic areas on a medium that has high resolution and does not alter the topography and magnetic performance of the hard-disk drives.